bursty

I recently brought my LS1 RX7 out to my new home in Breckenridge CO. It has a TRex cam, 1 3/4" LTs no cats, but otherwise its pretty stock. Its been sitting back home in St Louis for about 2 years where it was built and tuned. I'm trying to recall the specifics of the tune, but I seem to remember he said he had to tune the MAF out due to the large cam to get it to idle properly. Sound right?

Anyway, I've been doing a ton of searching trying to figure out what will have to be done to get it to drive and idle correctly at ~10,000' elevation. Most of the threads I have found only relate to Denvers altitude of 5500' or so. From what I gather, the MAF will do its best to adjust, but what about at my altitude? What about if my MAF was tuned out?

I'm thinking of taking the TRex out, getting some better flowing heads and a smaller cam and going from there. But in the mean time, any ideas on what I can do to at least make it driveable?

Thanks for any suggestion to a tuning noob

turbolx

A properly done tune shouldn't care about the altitude. (Hint: GM doesn't have a unique calibration for cars sold in CO, but they do test there!) Ideally, you would have both the MAF and VE tables dialed in to get the best of both worlds for accuracy under all conditions. Just remember that WOT won't be anywhere near 100kPa. When I was working in Breck/Frisco a few months ago, the best we saw was ~70kPa. I-70 through the Ike tunnel makes an interesting "dyno" to test the fringes of your tune.

bursty

bump

WeathermanShawn

iTrader: (1)

There might be a few gremlins you will have to work out. It is true that a perfect tune (VE & MAF) theoretically would not need adjusting. At key on, the PCM 'reads' BARO, and it is true your MAP's will be drastically lower.

At Idle, the MAP the vehicle was tuned at, will not be the same MAP it will Idle at 10K. If your tuner did not hit that particular RPM and MAP on the VE Table, Idle fueling may not be perfect.

Yes, I am Denver's altitude, but have done numerous jaunts up the Eisenhower Tunnel area. I normally log every run. Occasionally you get odd Trims, but IMO that is where a MAF and Closed-Loop help. My AFR stays locked at 14.7 all the way up. You can do it 'SD"..just easier to at least have closed-loop. The changes in air density are not as perfect as the 'Ideal Gas Law' will calculate. The ability to Trim will help.

If you have a wideband..best to recalibrate the O2 sensor when you install it. The O2 content is obviously less..

Those are a few thoughts. The bottom line is a good tune will handle it.

bursty

thanks for the info